Paradoxical Response of Parathyroid Hormone to Vitamin D-Calcium Supplementation in Indian Children.

OBJECTIVES: To investigate the effect of oral vitamin D-calcium supplementation on serum intact parathyroid hormone (PTH), calcium, phosphorous, and alkaline phosphatase (ALK-P) concentrations in children with habitually low calcium intakes. STUDY DESIGN: In this follow-up study to a randomized controlled trial that aimed to assess the effect of vitamin D-calcium supplementation on immunity, data related to dietary intake, anthropometry, and biochemistry [serum 25(OH)D and bone profile] were collected from 178 children-79 in the vitamin D group and 99 in the non-vitamin D group. RESULTS: Dietary calcium to phosphorus intake ratio was 0.4:1. Baseline serum 25(OH)D concentration was 58.2 ± 10.9 nmol/L; 66% children were vitamin D sufficient and none deficient. After supplementation, vitamin D group, compared with the non-vitamin D group, had significantly (P < .05) greater 25(OH)D (83.9 ± 30.1 nmol/L vs 58.3 ± 15.7 nmol/L), significantly greater PTH (6.7 ± 3.6 pmol/L vs 5.5 ± 3.2 pmol/L), and positive correlation (rs = 0.24) between serum 25(OH)D and PTH (vs negative correlation [rs = -0.1] in non-vitamin D group). Mean concentrations of serum bone measures in the vitamin D group were calcium (2.2 ± 0.1 mmol/L), phosphorus (1.7 ± 0.2 mmol/L), and ALK-P (178.7 ± 40.7 IU/L). At follow-up, 1-year post-supplementation, in the vitamin D group, PTH concentrations continued to remain high (but not significantly different from levels at 6 months), with low normal serum calcium, high normal phosphate, and ALK-P in reference range. CONCLUSIONS: In children who are vitamin D sufficient but with habitually low dietary calcium intake, vitamin D-calcium supplementation paradoxically and significantly increased serum PTH concentrations with no apparent effect on other bone biochemistry. Chronic low dietary calcium to phosphorus ratio is likely to have caused this paradoxical response.

Static cut-points of hypertension and increased arterial stiffness in children and adolescents: The International Childhood Vascular Function Evaluation Consortium.

Pediatric elevated blood pressure (BP) and hypertension are usually defined using traditional BP tables at the 90th and 95th percentiles, respectively, based on sex, age, and height, which are cumbersome to use in clinical practice. The authors aimed to assess the performance of the static cut-points (120/80 mm Hg and 130/80 mm Hg for defining elevated BP and hypertension for adolescents, respectively; and 110/70 mm Hg and 120/80 mm Hg for children, respectively) in predicting increased arterial stiffness. Using data from five population-based cross-sectional studies conducted in Brazil, China, Korea, and New Zealand, a total of 2546 children and adolescents aged 6-17 years were included. Increased arterial stiffness was defined as pulse wave velocity ≥sex-specific, age-specific, and study population-specific 90th percentile. Compared to youth with normal BP, those with hypertension defined using the 2017 American Academy of Pediatrics guideline (hereafter referred to as "percentile-based cut-points") and the static cut-points were at similar risk of increased arterial stiffness, with odds ratios and 95% confidence intervals of 2.35 (1.74-3.17) and 3.07 (2.20-4.28), respectively. Area under the receiver operating characteristic curve and net reclassification improvement methods confirmed the similar performance of static cut-points and percentile-based cut-points (P for difference > .05). In conclusion, the static cut-points performed similarly well when compared with the percentile-based cut-points in predicting childhood increased arterial stiffness. Use of static cut-points to define hypertension in childhood might simplify identification of children with abnormal BP in clinical practice.

Waist circumference percentiles in 2-18 year old Indian children.

OBJECTIVES: To develop reference percentile curves in Indian children for waist circumference (WC), and to provide a cutoff of WC percentile to identify children at risk for metabolic syndrome (MS). STUDY DESIGN: A multicenter, cross-sectional study was performed in 5 major Indian cities. Height, weight, and blood pressure (BP) were measured in 10,842 children (6065 boys). Elevated BP was defined as either systolic BP or diastolic BP >95th percentile. WC was measured with the child standing using a stretch-resistant tape. Sex-specific reference percentiles were computed using the LMS method which constructs reference percentiles adjusted for skewness. To determine optimal cutoffs for WC percentiles, a validation sample of 208 children was assessed for MS risk factors (ie, anthropometry, BP, blood lipids), and receiver operating characteristic (ROC) curve analysis was performed. RESULTS: Age- and sex-specific WC percentiles (5th, 10th, 15th, 25th, 50th, 75th, 85th, 90th, and 95th) are presented. WC values increased with age in both the boys and the girls. The median WC at age >15 years was greater in boys compared with girls. ROC analysis suggested the 70th percentile as a cutoff for MS risk (sensitivity, 0.84 in boys and 0.82 in girls; specificity, 0.85 in both boys and girls; area under the ROC curve, 0.88 in boys and 0.92 in girls). CONCLUSION: Age- and sex-specific reference curves for WC for Indian children and cutoff values of 70th WC percentile for screening for MS risk are provided.